Devices, softwares and methods with improved performance of acoustic echo canceler in VoIP communication

ABSTRACT

Devices, softwares and methods send a warning signal when a periodic signal is present in the audio content of a VoIP connection. In response to the warning signal, an acoustic echo canceller of an IP telephone discontinues its adapting process. A signaling network switch detects when a periodic signal is present in the audio content, and issues a warning signal. A signaling call manager device, when it transmits a tone that has periodicity, it also transmits a warning signal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to the field of network telephony, andmore specifically to devices, softwares and methods for improving aquality of a telephone call performed via a network.

2. Description of the Related Art

Packet switched networks, such as the internet, are increasingly usedfor voice communications. These communications are implemented usingtelephone devices that are connected to special network devices calledgateways. The voice data is typically exchanged under a special protocolcalled Voice over Internet Protocol (VoIP). Sometimes the telephones areIP (Internet Protocol) telephones, and the gateways are voice gateways.

The telephone devices sometimes have an acoustic echo canceller. Thisfeature minimizes how much echo of a voice communication is returned tothe other party.

Acoustic echo cancellers typically adapt to the acoustic characteristicsof the room. They tend to work intensively during the beginning of avoice communication, and often during it.

A problem with adaptive acoustic echo cancellers occurs during andimmediately after call setup, when an acoustic echo canceller works themost intensively. Call progress tones are heard which include DTMF (DualTone Multi Frequency) tones, and are given disproportionate weight.Adaptive acoustic echo cancellers adapt particularly well to those,because of their periodicity.

Such adapting generates problems, because later other tones might becanceled out, by being treated as echoes. Such other tones includethose, for example, of call waiting. In addition other sounds presentduring typical call set up (paper shuffling, finger tapping) tend tocause tones to fade in and out, especially in speakerphone applications.Fading in and out tends to be very annoying.

BRIEF SUMMARY OF THE INVENTION

The present invention overcomes these problems and limitations of theprior art.

Generally, the present invention provides devices, softwares and methodswith improved performance of acoustic echo canceller in VoIPcommunication. The invention sends a warning signal when a periodicsignal is present in the audio content. The acoustic echo cancellerdiscontinues its adapting process during that time, in response to thewarning signal.

A device according to the invention is a signaling network switch, whichdetects when a periodic signal is present in the audio content. Thesignaling network switch issues a warning signal for when the periodicsignal starts, and optionally also a clear signal when the periodicsignal ends.

Another device according to the invention is a signaling call managerdevice, which regularly assists in setting up a call between two networkdevices. When it transmits a tone (such as a tone command) that hasperiodicity, it also transmits a warning signal.

Another device made according to the invention is an IP telephone. TheIP telephone includes a codec for packetizing and unpacketizing theaudio signal. It also includes a speaker and a microphone. An acousticecho canceller senses the output of the microphone, and generates acanceling signal to cancel the echo. The acoustic echo canceller isadaptive for better performance. The telephone includes a detector fordetecting a warning signal from a cooperating signaling network switchor from a cooperating signaling call manager, and for outputting adisable signal in response to the warning signal. The acoustic echocanceller discontinues adapting responsive to the disable signal.

The invention offers the advantage that processing for detectingperiodic tones is performed at the resource rich voice gateway. This waythe telephone, having the fewer resources, is unfettered from having todetect a periodic tone.

The invention will become more readily apparent from the followingDetailed Description, which proceeds with reference to the drawings, inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A–FIG. 1D are diagrams of sample arrangements of a signalingnetwork switch and a signaling network call manager, alone and incombination, transmitting warning signals to a telephone that may bemade according to an embodiment of the invention.

FIG. 2 is a block diagram of components of a signaling network devicemade according to an embodiment of the invention.

FIG. 3 is a block diagram of components of a telephone made according toan embodiment of the invention.

FIG. 4 is a flowchart illustrating a method according to an embodimentof the present invention, which may be performed by a signaling networkswitch.

FIG. 5 is a flowchart illustrating another method according to anembodiment of the present invention, which may be performed by asignaling network call manager device.

FIG. 6 is a flowchart illustrating a method according to an embodimentof the present invention, which may be performed by a telephone that isadapted to receive a warning signal from either a signaling networkswitch performing the method of FIG. 4, or a call manager performing themethod of FIG. 5, or both.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

As has been mentioned, the present invention provides devices, softwaresand methods with improved performance of acoustic echo canceller in VoIPcommunication. This is for communication through networks where data istransmitted in packet form. The invention is now described in moredetail.

Referring now to FIG. 1A, aspects of the invention are described in abroad overview form. The invention relates to network telephony, wheredata is transmitted through a network, such as through a network 110.Network 110 may be an Internet Protocol (IP) network 110, also known asIP Cloud 110, such as the internet or a private network.

A signaling network switch 120 made according to an embodiment of theinvention may be placed in IP Cloud 110 as a node. Device 120 may be agateway, voice gateway, bridge, conference bridge, a router, or othernetwork switch.

A telephone 130 may use switch 120 to dial an IP telephone 140.Telephone 140 may or may not be made according to the invention.

Telephone 130 uses switch 120 by calling it. This means establishing atelephone connection 135 with it, through the Public Switched TelephoneNetwork (PSTN).

In turn, switch 120 establishes a communication link 142 through IPCloud 110 with telephone 140. Link 142 is called a communicationconnection, because voice data will be transmitted through it.

In some embodiments, link 142 may be established directly with telephone140, without the intervention of other devices, such as call managers.For example, certain classes of phones (in the place of telephone 140)may establish contact directly with switch 120. Such phones includethose powered by SIP (Session Initiation Protocol). SIP is acutting-edge Internet protocol that enables web developers to createadvanced telephony and multimedia applications, using familiar Internetprotocols and web tools.

In other embodiments, link 142 may be established as follows. Switch 120first establishes a link 144 through IP Cloud 110 with a network callmanager device 146. Manager 146 is shown in dashed lines in FIG. 1A,because it need not be made according to the invention, for the benefitof the invention to be realized in this embodiment. Link 144 is called anetwork call manager connection, because it does not transmit voicedata. Then manager 146 establishes a second network call managerconnection 148 with device 140. Then manager 146 assists switch 120 toestablish communication connection 142 with telephone 140, and maintainit.

An overall connection may thus be established between phones 130, 140.The overall connection is via the combined communication links 135 and142. The users of phones 130, 140 may speak to each other. Their voicesare carried as data packets 155, 156 through network 110.

Importantly, switch 120 analyzes the encoded audio that is contained indata packets 155, 156. Preferably this is performed by looking ahead inthe stream, before time comes to transmit.

If switch 120 detects that a periodic tone is included in the audio,switch 120 sends a warning signal. The periodicity may be a singleperiodicity, or a double periodicity, such as that of a DTMF (Dual ToneMulti Frequency) signal.

The warning signal may be transmitted with the transmitted voice datapackets 155, 156. The warning signal may be out of band, with respect tothe voice data, such as a named signaling event (NSE). Or it may be anin-band signal.

In another embodiment, the warning signal may be encoded in a warningpacket 172. In one more embodiment, when switch 120 detects the end ofthe periodic tone, it also sends a clear signal CS. Signal CS may betransmitted by means of a clear packet 178.

Switch 120 sends the warning packet ahead of at least some of the voicepackets 155, 156 that contain the encoded periodic tone. This wayreceiving telephone 140, if made according to the invention, will havethe opportunity to turn off the adaptation of its acoustic echocanceller.

Switch 120 is the preferred device for performing the analysis of theaudio, to determine whether a periodic tone is included. That is becauseswitch 120 is encoding the audio in the first place, and is resourcerich.

Switch 120 is preferably by designation the entry point in the network.Since there is only one, such a designation will prevent duplication ofwarning signals. In addition, it will ensure that generation of thewarning signal takes place at the same device where encoding occurs, forensuring the advantage mentioned above. In other, equivalentembodiments, switch 120 is a convenient point of access of IP telephone140.

Referring now to FIG. 1B, a signaling call manager device 180 madeaccording the invention is used. In the embodiment of FIG. 1B, a networkgateway 122 is used, that need not be made according to the invention.

Telephone 130 may establish a connection 136 with gateway 122 throughthe PSTN. In turn, gateway 122 establishes a communication connection145 through IP Cloud 110 with device 140.

Link 143 may be established as follows. Gateway 122 first establishes anetwork call manager connection 143 through IP Cloud 110 with networkcall manager device 180. Then manager 180 establishes a second networkcall manager connection 149 with device 140. Then manager 180 assistsgateway 122 establishing communication connection 145 with telephone140, and maintain it.

An overall connection may thus be established between phones 130 and140. The overall connection is via the combined communication links 136and 145. The users of phones 130, 140 may speak to each other. Theirvoices are carried as data packets 155, 156 through network 110.

Importantly, while manager 180 is setting up the call, and alsothereafter, it generates tones or tone generation commands. Some ofthese tones are periodic, and some with double periodicity.

Manager 180 also generates and sends a warning signal, to be received atleast by telephone 140. The warning signal is encoded in a warningpacket 182. When received, telephone 140 is thus given the option ofturning off its acoustic echo canceller.

In the embodiment of FIG. 1B, warning packet 182 is transmitted throughlink 149. Equivalently, warning packet 182 may be transmitted firstthrough link 143, and then through link 145, as is seen below.

In the preferred embodiment, manager 180 also encodes a time duration ofthe periodic signal along with the warning signal.

Referring now to FIG. 1C, one more arrangement according to theinvention is shown. Both a signaling network switch 120 and a signalingcall manager 180 are used. Between them they establish a link 141. Theneither one may generate a warning signal for device 140.

In the embodiment of FIG. 1C, manager 180 generates a warning packet182, and transmits it to switch 120. In turn, switch 120 retransmits itto telephone 140.

Referring now to FIG. 1D, yet another arrangement according to theinvention is shown. An IP telephone 170 dials IP telephone 140,establishing a communication connection 176 between them. Link 176 isestablished by first establishing a network call manager link 172 withsignaling call manager 180 made according to the invention. Then manager180 may send its warning packet 182 when a periodic tone will be sent.

Referring now to FIG. 2, a device 210 made according to an embodiment ofthe invention is described in more detail. The information given herefor device 210 may be used for constructing either signaling networkswitch 120, or signaling call manager 180 according to the invention.

Device 210 has a network interface 220 for interfacing with a network,such as network 110. Interfacing is by establishing links forcommunication with other devices in the network.

Device 210 also has a processor 230 coupled with network interface 220.Processor 230 may be implemented as a digital signal processor, CentralProcessing Unit (CPU), or any other equivalent way known in the art.Device 210 additionally includes a memory 240, on which a program 250may reside. Functions of processor 230 may be controlled by program 250,as will become apparent from the below.

Referring now to FIG. 3, an IP telephone 140 made according to anembodiment of the invention is described in more detail.

IP telephone 140 includes a network interface 305 for interfacing with anetwork, such as network 110. Interfacing is by establishing links forcommunication with other devices in the network.

IP telephone 140 includes a codec 310. Codec 310 includes a decoder 320.Decoder 320 is for decoding data packets incoming from network interface305. In response, decoder 320 outputs an incoming audio signal IAS.Signal IAS represents decoded sound that was previously encoded inpackets 155, 156.

IP telephone 140 also includes a speaker 330. Speaker 330 plays out aprocessed incoming audio signal PIAS for the user of IP telephone 130.In other words, speaker 330 receives a processed incoming audio signalPIAS, and plays out the represented sound.

IP telephone 140 additionally includes a microphone 340. Microphone 340is for converting sound into an outgoing audio signal OAS. That isprovided for the voice of the user of IP telephone 140.

Codec 310 also includes an encoder 350. Encoder 350 is for encoding theprocessed outgoing audio signal POAS in data packets (not shown in FIG.3). These encoded data packets may then be transmitted to networkinterface 305.

IP telephone 140 further includes an acoustic echo canceller 360.Canceller 360 is for canceling sound that was generated by IncomingAudio Signal IAS. More particularly, an aspect of outgoing audio signalOAS is generated from converting sound played out by speaker 330.Canceller 360 is adapted for adapting to that aspect, so as to bettercancel it. Signal PIAS is a result of canceller 360 process, such asattenuation, of signal IAS. Signal POAS is a result of canceller 360process, which may be filtering and may be attenuation. Encoder 350therefore generally does not retransmit back to the network any soundsthat came from the network.

IP telephone 140 also includes a warning signal detector 370, which isalso known simply as detector 370. Detector 370 is adapted to detect awarning signal WS from the incoming data packets, which was generatedfrom the cooperating signaling network switch 120. Detector 370 isadapted to generate a Disable signal DS in response to warning signalWS.

Importantly according to the invention, acoustic echo canceller 360discontinues adapting responsive to disable signal DS. This will preventcanceller 360 from adapting to a periodic signal.

In one embodiment of the invention, detector 370 is adapted to detect aclear signal CS from the data packets. Detector 370 may discontinuedisable signal DS responsive to clear signal CS, and thus re-enablecanceller 360 to resume adapting.

In another embodiment of the invention, detector 370 is adapted todetermine a time duration encoded in the warning signal WS. Encoding maybe either explicit or as a protocol. That is a time duration of theperiodic sound in the audio. Detector 370 is further adapted todiscontinue disable signal DS after the time duration. Again, this willre-enable canceller 360 to resume adapting.

Most cancellers attenuate adversely the signal they process. Anadvantage of the invention is that, when canceller 360 discontinuesadapting, it also discontinues the adverse attenuation.

It is readily apparent that the present invention may be implemented byone or more devices that include logic circuitry. It may also beimplemented by a device that includes a dedicated processor system,which may include a microcontroller or a microprocessor. For example,codec 310, canceller 360 and detector 370 may be implemented in aDigital Signal Processing (DSP) block 380.

The invention additionally provides methods, which are described below.Moreover, the invention provides apparatus that performs, or assists inperforming the methods of the invention. This apparatus may be speciallyconstructed for the required purposes, or it may comprise ageneral-purpose computer selectively activated or reconfigured by acomputer program stored in the computer. The methods and algorithmspresented herein are not necessarily inherently related to anyparticular computer or other apparatus. In particular, variousgeneral-purpose machines may be used with programs in accordance withthe teachings herein, or it may prove more convenient to construct morespecialized apparatus to perform the required method steps. The requiredstructure for a variety of these machines will appear from thisdescription.

Useful machines or articles for performing the operations of the presentinvention include general-purpose digital computers or other similardevices. In all cases, there should be borne in mind the distinctionbetween the method of operating a computer and the method of computationitself. The present invention relates also to method steps for operatinga computer and for processing electrical or other physical signals togenerate other desired physical signals.

The invention additionally provides a program, and a method of operationof the program. The program is most advantageously implemented as aprogram for a computing machine, such as a general-purpose computer, aspecial purpose computer, a microprocessor, etc.

The invention also provides a storage medium that has the program of theinvention stored thereon. The storage medium is a computer-readablemedium, such as a memory, and is read by the computing machine mentionedabove.

A program is generally defined as a sequence of steps leading to adesired result. These steps, also known as instructions, are thoserequiring physical manipulations of physical quantities. Usually, thoughnot necessarily, these quantities take the form of electrical ormagnetic signals capable of being stored, transferred, combined,compared, and otherwise manipulated or processed. When stored, they maybe stored in any computer-readable medium. It is convenient at times,principally for reasons of common usage, to refer to these signals asbits, data bits, samples, values, elements, symbols, characters, images,terms, numbers, or the like. It should be borne in mind, however, thatall of these and similar terms are associated with the appropriatephysical quantities, and that these terms are merely convenient labelsapplied to these physical quantities.

This detailed description is presented largely in terms of flowcharts,display images, algorithms, and symbolic representations of operationsof data bits within a computer readable medium, such as a memory. Suchdescriptions and representations are the type of convenient labels usedby those skilled in programming and/or the data processing arts toeffectively convey the substance of their work to others skilled in theart. A person skilled in the art of programming may use this descriptionto readily generate specific instructions for implementing a programaccording to the present invention. For the sake of economy, however,flowcharts used to describe methods of the invention are not repeated inthis document for describing software according to the invention.

Often, for the sake of convenience only, it is preferred to implementand describe a program as various interconnected distinct softwaremodules or features, collectively also known as software. This is notnecessary, however, and there may be cases where modules areequivalently aggregated into a single program with unclear boundaries.In any event, the software modules or features of the present inventionmay be implemented by themselves, or in combination with others. Eventhough it is said that the program may be stored in a computer-readablemedium, it should be clear to a person skilled in the art that it neednot be a single memory, or even a single machine. Various portions,modules or features of it may reside in separate memories, or evenseparate machines. The separate machines may be connected directly, orthrough a network, such as a local access network (LAN), or a globalnetwork, such as the Internet.

In the present case, methods of the invention are implemented by machineoperations. In other words, embodiments of the program of the inventionare made such that they perform methods of the invention that aredescribed in this document. These may be optionally performed inconjunction with one or more human operators performing some, but notall of them. As per the above, the users need not be collocated witheach other, but each only with a machine that houses a portion of theprogram. Alternately, some of these machines may operate automatically,without users and/or independently from each other.

Methods of the invention are now described.

Referring now to FIG. 4, a flowchart 400 is used to illustrate a methodaccording to an embodiment of the invention. The method of flowchart 400may be performed by a signaling network switch.

According to a box 410, a first connection is established through anetwork. The first connection is with a first device, such as connection142 with IP telephone 140 in FIG. 1A.

According to a next box 420, a second connection is established with asecond device, such as connection 135 with telephone 130.

According to a next box 430, audio content is received through thesecond connection. This is either in the form of a signal, or in theform of encoded audio, carried in data packets.

According to a next box 440, the audio content is analyzed for periodicsignals. This is preferably implemented by looking ahead, such as in thestream of data packets.

According to a next box 450, it is inquired whether the start of aperiodic signal is detected as a result of the analysis.

If not, then according to a next box 455, data packets are transmittedthrough the first connection, which include the received audio inencoded form. Execution then returns to box 430.

If yes, then according to a next box 460, a warning signal istransmitted through the first connection. It may be included in awarning packet, or be merged with the audio content.

According to a next box 470, data packets are transmitted through thefirst connection, which include the received audio in encoded form. Thenadditional audio content is received, and analyzed for an ending of theperiodic signal.

According to a next box 480, it is inquired whether an ending of theperiodic signal is detected. If not, then execution returns to box 470.

If yes, then according to a next box 490, a clear signal is transmittedthrough the first connection. It may be transmitted as a clear packet.

Referring now to FIG. 5, a flowchart 500 is used to illustrate a methodaccording to an embodiment of the invention. The method of flowchart 500may be performed by a network call manager device, assisting two devicesestablish a VoIP communication connection in a packet switched network.

According to a box 510, a first network call manager connection isestablished through the network. The first connection is with a firstdevice.

According to a next box 520, a second network call manager connection isestablished with a second device.

According to a next box 530, the first device and the second device areassisted in having a communication connection through the network.

According to a next box 540, a first periodic signal is generated, or aninstruction is generated for a second periodic signal to be generated byone of the first and second devices. In the first case, the firstperiodic signal is generated by the call manager. In the second case,the instruction is for the first or the second device to generate asecond periodic signal. In either case, the first or the second periodicsignal may have double periodicity. It may be part of the call setup, ora call waiting tone for one of the parties, etc. Although generated, thefirst periodic signal or the second periodic signal is preferably notsent yet. The following description proceeds equally for either one ofthe two signals.

According to a next box 570, a time duration of the periodic signal isencoded in a warning signal. In the preferred embodiment, this takesplace as follows. According to a box 550, the type of the periodicsignal is identified. It might be one of some of the known types ofperiodic signals. According to a subsequent box 560, the periodic signalduration is determined from the identified type. This may be performedby looking up a table of the known types of periodic signals.

According to a next box 580, the warning signal is transmitted throughone of the first and second network call manager connections.

According to a next box 590, the first periodic signal is transmittedthrough one of the first and second network call manager connections. Inthe situation where, in box 540, an instruction was generated forgenerating a second periodic signal, then it is the instruction that istransmitted.

Referring now to FIG. 6, a flowchart 600 is used to illustrate a methodaccording to another embodiment of the invention. The method offlowchart 600 may be performed by a telephone, especially onecooperating with either a signaling network switch implementing themethod of flowchart 400, or a signaling call manager implementing themethod of flowchart 500.

According to an optional box 610, a call manager connection isestablished with a call manager device in a network. The call managerconnection may be connection 144, established with device 120 in network110 of FIG. 1A or connection 143 of FIG. 1B.

According to a next box 620, a communication connection is establishedwith a device in a network. The communication connection may beconnection 142 of FIG. 11A or connection 145 of FIG. 1B.

According to a next box 630, data packets are received through thecommunication connection. The data packets contain encoded audio.

According to a next box 640, a warning signal is received. The warningsignal warns that a periodic tone is encoded in the audio. The warningsignal may be received either through the call manager connection, orthrough the communication connection, as the case may be.

According to a next box 650, the adaptive acoustic echo canceller isdisabled in response to the warning signal. If performed in hardware,this might be by issuing a disable signal. If in software, the disablesignal may be by setting a flag.

According to an optional next box 660, it is determined whether thewarning signal contains a time duration.

If yes, then according to a next box 670, a time duration of theperiodic tone or periodic signal is determined. According to a next box675, the device waits for the time duration that was determined above.According to a next box 680, the adaptive acoustic echo canceller isre-enabled in response to the clear signal.

Re-enabling according to box 680 may be performed by performing theinverse of box 650. For example, if a disable signal has been issued, itmay be recalled. If a disable flag has been set, it may be reset.

If, on the other hand, at box 660 it is determined that the warningsignal does not contain a duration, then the device waits until,according to a next box 690, a clear signal is received through thefirst telephone connection. Execution then continues with box 680.

While the present description is given in a context of a two party call,such is only by example, and not by limitation. Indeed, the devices,softwares and methods of the invention may also be used in scenariawhere more parties participate, such as conference calling.

In addition, while the present description is given in a context of avoice call, such is only by example, and not by limitation. Indeed, thedevices, softwares and methods of the invention may also be used inscenaria of video calls that have a sound component.

A person skilled in the art will be able to practice the presentinvention in view of the description present in this document, which isto be taken as a whole. Numerous details have been set forth in order toprovide a more thorough understanding of the invention. In otherinstances, well-known features have not been described in detail inorder not to obscure unnecessarily the invention.

While the invention has been disclosed in its preferred form, thespecific embodiments as disclosed and illustrated herein are not to beconsidered in a limiting sense. Indeed, it should be readily apparent tothose skilled in the art in view of the present description that theinvention may be modified in numerous ways.

The inventor regards the subject matter of the invention to include allcombinations and subcombinations of the various elements, features,functions and/or properties disclosed herein.

The following claims define certain combinations and subcombinations,which are regarded as novel and non-obvious. Additional claims for othercombinations and subcombinations of features, functions, elements and/orproperties may be presented in this or a related document.

1. A signaling network processing device comprising: a network interfacefor coupling to a network; and a processor coupled with the networkinterface, wherein the processor is adapted to: establish a call managerconnection with a call manager; exchange signaling messages over thecall manager connection to establish a communicative connection with anendpoint other than the call manager, the signaling messages notincluding any voice data; analyze the received audio content to identifya portion having a periodic signal; generate a warning packet to signalthe endpoint to turn off acoustic echo canceller adaptation; generate aclear packet to signal the endpoint to turn on acoustic echo cancelleradaptation; transmit a representation of the received audio content; andtransmit the warning packet and the clear packet directly to theendpoint separately and independently from the representation ofreceived the audio content.
 2. The signaling network processing deviceof claim 1, wherein analyzing the received audio content is performed bylooking ahead.
 3. The signaling network processing device of claim 1,wherein the periodic signal has a double periodicity.
 4. The signalingnetwork processing device of claim 1, wherein the warning signal isin-band.
 5. The signaling network processing device of claim 1, whereinthe warning signal is out of band.
 6. The signaling network processingdevice of claim 5, wherein the warning signal is a named signalingevent.
 7. The signaling network processing device of claim 1, theprocessor is further adapted to: determine a duration of the periodicsignal; and encode the duration in the warning packet.
 8. A signalingnetwork call manager comprising: a network interface for coupling to anetwork; and a processor coupled with the network interface, wherein theprocessor is adapted to establish a first network call managerconnection with a network device, the first network call managerconnection being an out of band connection; establish a second networkcall manager connection with a telephone endpoint including an IPtelephone with an acoustic echo canceller, the second call managerconnection being an out of band connection; exchange signaling over thefirst and second network call manager connections to establish acommunicative connection through a packet switched network to thetelephone endpoint, the communicative connection being an in bandconnection and used by the network device to transmit voice data to thetelephone endpoint; generate one of a first periodic signal and aninstruction for a second periodic signal to be played by the telephoneendpoint; encode a time duration of one of the first periodic signal andthe second periodic signal in a warning signal; transmit the warningsignal in at least one packet through the second network call managerconnection to be received by the IP telephone to control the acousticecho canceller; and transmit the generated one of the first periodicsignal and the instruction through the second network call managerconnection; wherein the voice data is not transmitted through either thefirst or second network call manager connection.
 9. The signalingnetwork call manager of claim 8, wherein one of the first and secondperiodic signals has a double periodicity.
 10. The signaling networkcall manager of claim 8, the processor is further adapted to: identify atype of one of the first periodic signal and the second periodic signal;and determine the time duration from the identified type.
 11. A devicecomprising: means for establishing a signaling path with a call manager;means for exchanging communications over the signaling path with thecall manager to establish a communicative connection through a packetswitched network to an endpoint, the endpoint being physically separatefrom the call manager; means for identifying a periodic signal includedin received audio content; means for identifying a duration of theperiodic signal; means for generating a warning packet that encodes theduration of the periodic signal; and means for transmitting the warningpacket to the endpoint to control an echo canceller.
 12. The device ofclaim 11, wherein the means for identifying the periodic signal isperformed by looking ahead.
 13. The device of claim 11, wherein theperiodic signal has a double periodicity.
 14. The device of claim 11,wherein the warning packet is transmitted in-band.
 15. The device ofclaim 11, wherein the warning packet is transmitted out of band.
 16. Thedevice of claim 15, wherein the warning signal is a named signalingevent.
 17. The device of claim 11, further comprising: means fordetermining an ending of the periodic signal; and means for transmittinga clear signal corresponding to the ending.
 18. A device comprising:means for establishing a first network call manager connection with agateway that couples a non packet switched network to a packet switchednetwork; means for establishing a second network call manager connectionwith a telephone endpoint; means for exchanging communications over thefirst and second network call manager connections to assist a gateway inestablishing a call through the packet switched network to the telephoneendpoint; means for generating one of a first periodic signal and aninstruction for a second periodic signal to be played by the telephoneendpoint; means for encoding a time duration of one of the firstperiodic signal and the second periodic signal in a warning signal;means for transmitting the warning signal in at least one packet throughthe second network call manager connection to be received by thetelephone endpoint to control an echo canceller; and means fortransmitting the generated one of the first periodic signal and theinstruction through the second network call manager connection to bereceived by the telephone endpoint.
 19. The device of claim 18, whereinone of the first and second periodic signals has a double periodicity.20. The device of claim 18, further comprising: means for identifying atype of one of the first periodic signal and the second periodic signal;and means for determining the time duration from the identified type.21. An article comprising: a storage medium, said storage medium havingstored thereon instructions, that, when executed by at least one device,result in: exchanging signaling messages over a call manager connectionto establish a communicative connection with an endpoint; analyzingreceived audio content to determine whether the received audio contentincludes a periodic signal; transmitting to the endpoint through thecommunicative connection data packets representing the received audiocontent; and transmitting to the endpoint through the communicativeconnection a warning packet and a clear packet to respectively signal abeginning and an end of the periodic signal included in the data packetsand to control an echo canceller; wherein the warning and clear packetsare transmitted from the at least one device to the endpointindependently of the data packets representing the received audiocontent.
 22. The article of claim 21, wherein analyzing the receivedaudio content is performed by looking ahead.
 23. The article of claim21, wherein the instructions further result in: determining a durationof the periodic signal; and encoding the duration in the warning packet.24. An article comprising: a storage medium, said storage medium havingstored thereon instructions, that, when executed by at least one device,result in: establishing a first network call manager connection with anetwork device; establishing a second network call manager connectionwith a telephone endpoint including an IP telephone with an acousticecho canceller; exchanging communications over the second network callmanager connection to cause a communicative connection to be establishedfrom the network device through a packet switched network to thetelephone endpoint; generating one of a first periodic signal and aninstruction for a second periodic signal to be played by the telephoneendpoint; encoding a time duration of one of the first periodic signaland the second periodic signal in a warning signal; transmit the warningsignal in at least one packet through the second network call managerconnection to be received by the IP telephone to control the acousticecho canceller; and transmitting the generated one of the first periodicsignal and the instruction through the second network call managerconnection.
 25. The article of claim 24, wherein one of the first andsecond periodic signals has a double periodicity.
 26. The article ofclaim 24, wherein the instructions further result in: identifying a typeof one of the first periodic signal and the second periodic signal; anddetermining the time duration from the identified type.
 27. A method ofoperating a gateway that separates a packet switched network and acircuit switched network, said method comprising: exchanging signalingover the packet switched network and between the gateway and a callmanager to establish a connection with an endpoint through the packetswitched network; receiving audio content from the circuit switchednetwork; transmitting to the endpoint through the connection datapackets that contain an encoded form of the received audio content;analyzing the audio content for a periodic signal; and transmitting awarning signal through the connection over the packet switched networkwhen a periodic signal is identified, the warning signal controlling anecho canceller; wherein the data packets and the warning signal areaddressed independently of an address for the call manager.
 28. Themethod of claim 27, wherein analyzing the audio content is performed bylooking ahead.
 29. The method of claim 27, wherein the periodic signalhas a double periodicity.
 30. The method of claim 27, wherein thewarning signal is in-band.
 31. The method of claim 27, wherein thewarning signal is out of band.
 32. The method of claim 31, wherein thewarning signal is a named signaling event.
 33. The method of claim 27,further comprising: determining an ending of the periodic signal; andtransmitting a clear signal corresponding to the ending.
 34. The methodof claim 27, further comprising: determining a duration of the periodicsignal; and encoding the duration in the warning signal.
 35. A methodcomprising: establishing a first network call manager connection thatdoes not transmit voice data with a network device; establishing asecond network call manager connection that does not transmit voice datawith an endpoint; exchanging Session Initiation Protocol (SIP) signalingmessages over the first and second call manager connections to assistthe network device in establishing a communication connection with theendpoint through a packet switched network; generating one of a firstperiodic signal and an instruction for a second periodic signal to beplayed by an IP telephone associated with the endpoint; encoding a timeduration of one of the first periodic signal and the second periodicsignal in a warning signal; transmitting the warning signal in at leastone packet through the second call manager connection to be received bythe IP telephone to control an acoustic echo canceller; and transmittingthe generated one of the first periodic signal and the instructionthrough the second call manager connection.
 36. The method of claim 35,wherein one of the first and second periodic signals has a doubleperiodicity.
 37. The method of claim 35, further comprising: identifyinga type of one of the first periodic signal and the second periodicsignal; and determining the time duration from the identified type. 38.The signaling network processing device of claim 1 wherein the endpointreceives the representation of the audio content and the packetsseparately and independently.